a. Field of the Invention
The present invention relates to a molded article of fiber-reinforced thermoplastic which is light weight and excellent in mechanical strengths and can be utilized for various fields including automobile parts such as bumper backup beam, door beam and seat shell, structural materials and machinery parts, and also relates to a process for preparing the same.
b. Description of the Prior Art
Fiber-reinforced thermoplastics (FRTP) are light weight and excellent in mechanical strengths and hence are used in the form of molded article for automobile parts, structural materials, machinery parts and other fields. The molded article is prepared by using a plate material essentially consisting of thermoplastic resin and fibrous reinforcement as raw materials and by carrying out stamping and other molding processes.
In the stamping process, the plate material is heated above the melting temperature of the resin to provide fluidity for the plate material itself. Thereafter, the plate material is placed in a mold maintained at a temperature lower than the melting temperature of the resin, the mold is immediately closed, and cooling and forming are simultaneously carried out to obtain a molded article of an arbitrary form. The process, however, is liable to cause deformation or cracks in a specific portion of the molded article particularly in the case of molding a complex shaped article. Consequently, restriction has been imposed upon the use of the material.
Another process has been tried to use a sheet prepreg containing a unidirectionally arranged fiber or a woven cloth impregnated with a thermoplastic resin as a raw material of the molded article. However, the molded article prepared from the sheet prepreg cannot overcome the above problems of deformation and cracks, although strengths are generally higher than the article prepared from the plate material. Additionally, the sheet prepreg is more expensive than the plate material. Constitution of the whole molded article with the sheet prepreg leads to higher production cost of the molded article.
In order to solve the problems of deformation and cracks, a further process increases the overall strength of the molded article by selecting a specific resin and/or fibrous reinforcement which constitute the plate material. For example, generation of deformation and cracks can be prevented by selection of high performance engineering plastics and/or carbon fiber. However, the plastics and fibrous reinforcement are very expensive. Consequently, it is unfavorable in economy to constitute the whole molded article by such resin and fibrous reinforcement, because the portion required-to prevent cracks and deformation is only a part of the molded article.
The object of the present invention is to provide a molded article having no deformation or cracks at a specific portion and a process for preparing the article even in molding a plate material essentially consisting of a thermoplastic resin and a fibrous reinforcement.
The above object can be achieved by the process and molded article described below.
A process for preparing a molded article of fiber-reinforced plastic having an optional configuration by using a plate material consisting essentially of a fibrous reinforcement and a thermoplastic resin, comprising the steps of previously setting-up, on the plate material and/or in a mold, a sheet prepreg obtained by impregnating a unidirectionally arranged fiber or woven cloth with a thermoplastic resin in areas where the fibrous reinforcement does not follow the flow of the resin well or in areas where special reinforcement is required and successively carrying out integral molding to obtain said article.
A molded article of fiber-reinforced plastic obtained by molding a plate material consisting essentially of a fibrous reinforcement and a thermoplastic resin, comprising subjecting a sheet prepreg obtained by impregnating a unidirectionally arranged fiber or woven cloth with a thermoplastic resin to mold it integrally with a portion of the plate material.
In accordance with the present inventions, the molded articles reinforced strengths at ribbed portions and narrow sections, and various molded articles of large to small volumes can be prepared without deformation and cracks.